Adjustable switch actuator



Feb. 14, 1967 T. Y. KoRsREN 3,304,382

ADJUSTABLE SWITCH ACTUATOR Filed Dec. 2, 1964 s Sheets-Sheet 1 Feb. 14, 1967 "r. Y. KORSGREN 3,304,382

ADJUSTABLE SWITCH ACTUATOR Filed Dec. 2, 1964 3 Sheets-Sheet 2 Feb. 14, 1967 Filed Dec. 2, 1964 T. Y. KORSGREN 3,304,382

ADJUSTABLE SWITCH ACTUATOR United States Patent Cfifice 135M582 Patented Feb. 14, 1967 3,304,382 ADJUSTABLE SWHTCH ACTUATOR Theodore Yngve Korsgren, Cary, lill., assignor to International Telephone and Telegraph Corporation, New York, N .Y., a corporation of Maryland Filed Dec. 2, 1%4, Ser. No. 415,252 6 Claims. (Cl. 209-67) This invention relates to snap acting switches and more particularly to switches having an adjustable operating point.

Many different kinds of devices may be used to open or close an electrical circuit responsive to any other equipment which provides an excursion of a mechanical part. One such device is a snap action switch such as described herein. It should be understood, however, that the invention is not restricted to such snap switches. Moreover, to facilitate a description of the inventive principles, it will be convenient to explain how the switch is used in conjunction with specific equipment (a thermostat having a bi-metal strip which bends as it expands or contracts as a function of temperature changes). However, this invention is not limited to this particular or to any other specific-usage, but may be used in conjunction with any power element such as a bi-metal blade or diaphragm, bellows, expansion liquids or gases, or the like.

interposed between the switch and power element is a series of mechanical parts which serve to transmit motion from the power element to the switch. The motion is a mechanical excursion which operates the switch. The exact nature of the mechanical parts is unimportant; they could be calibration means, force or motion multiplying linkage, cams, range setting devices, or the like. Heretofore, it has been customary to design a different set of such mechanical parts for every different kind of a control device. Obviously, there would be a great savings if this variety of mechanical parts could be replaced by a single simple switch design utilizing only a few standardized piece parts.

To provide such a switch design, it is convenient to have a calibration means for selecting a range of adjustments. The switch may then be set, within the adjustment range, to any suitable operating point which meets a users demands. For instance, in the thermostat ex ample, the adjustment range might be 5090 and the operating point might be 75.

Unfortunately, however, when efforts have been made to provide such a single switch, the calibration and operating point selection devices have caused as many problems as they have solved. It has not been possible to change one characteristic of a switch without also changing other charatceristics of the switch; thus, adjustments became time consuming trial-and-error operations. Also, the calibrating mechanism has added to the inertia of the switch and made it too bulky and sluggish.

Accordingly, an object of the invention is to provide new and improved electrical control devices, such as snap action switches having an adjustable operating point. In this connection, an object is to provide a snap action switch having an infinite number of adjustment ranges. A further object is to provide a switch of a design such that a single type of construction may be used to eliminate or replace many switch-mechanical linkage combinations.

Another object is to provide a snap action switch having means whereby a single characteristic of the switch may be adjusted without affecting any other characteristic of the switch.

Yet another object of the invention is to provide extremely low cost, high quality, snap action switches.

More particularly, an object is to provide snap action switches made from standardized piece parts fabricated by general purpose machine tools.

In accordance with one aspect of this invention, these and other objects are accomplished by a switch having an adjustable operating point. An actuator in the form of a pin plunger is arranged to push against the spring for moving the spring from its normal to an otf-normal position. The pin plunger assembly includes an actuator foot having a threaded pin attached thereto. An elongated actuator nut having a threaded bore is turned onto the threaded pin. Thus, the effective length of the actua tor pin plunger assembly is determined by the number of turns given the nut. This, is turn, fixes the travel distance required by the sensor power unit to operate the switch. Also, mounted on the switch housing is an adjustment range dial having a smooth central passage. The cross sections of the actuator nut and passage are complementary so that the nut slides freely through the passage, but turns as the range dial is turned. This way the dial may be turned to select any operating point by adjusting the effective length of the pin plunger. How ever, the weight of the range dial does not add to the inertia of the pin plunger assembly.

By way of definition, the actuator may always move through a mechanical excursion having the same fixed distance. However, by adjusting the length of the actuator, the switch may be made to operate at an earlier or later point in the excursion. Thus, if reference is made herein to adjusting the stroke, it should be understood that this means adjusting the point in the stroke where the switch operates.

' The above mentioned and other objects and features of this invention and the manner of obtaining them will be come more apparent, and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, in which:

FIGS. 1A and 1B are two perspective views of the side and top (respectively) of a switch constructed according to the invention;

FIG. 2 is an exploded view of the principal elements of the switch;

FIG. 3 is a cross section view of a box mounting the switch in an exemplary thermostat arrangement;

FIG. 4 is a side view of an exemplary snap action spring in a normal position; and

FIG. 5 is a side view of the same exemplary snap action spring in an off-normal position.

A switch embodying the invention is shown in the drawings as having three principal sub-assemblies: a two part housing 20, an actuator and range dial 21, and a selfbiasing, monostable leaf spring assembly 22. The election to show a snap action switch and a monostable leaf spring are for convenience of description; other devices may also be used.

The housing may be constructed from any suitable material, such as a thermal setting plastic. It has two parts, an upper half 23 and a lower half 24 which fit together to provide an enclosure that is protected against contaminants. A hole 25 extends through the upper housing half 23 to allow a pin plunger of an actuator to act upon the leaf spring assembly 22 which is mounted inside the housing. A range dial mechanism 26 is mounted on the housing 23 adjacent the pin plunger. During manufacture, the range dial is secured in any one of an infinite number of positions, relative to the pin plunger, in order to select an adjustable range of operations.

The lower half 24 of the housing includes two mounting holes 27, 28 for securing the snap acting switch to any other elements. Also, the lower housing half 24 has molded or inserted therein in three studs 2931 which (3 act both as electrical terminals extending through the housing and as rivets for securing the leaf spring assembly 22 and its associated contacts to the housing. Any suitable means (not shown) may be provided for holding together the two halves.

The actuator assembly includes an actuator or presser foot plate 35 having an upstanding threaded pin 36 attached thereto. An elongated threaded nut 37 is turned on to the threaded pin. This way, the operating point in the actuating .stroke is changed by the simple expedient of turning the nut one way or the other to give the actuator pin plunger 36, 37 any desired length, and therefore a desired length of travel prior to switch operation.

The range dial mechanism 26 includes a circular plate 40 having a scale 41 printed or otherwise formed thereon. The scale may have any convenient divisions; usually simple degree marking will be adequate. The plate 40 is attached to the housing half 23 by means of a bushing 42 having a smooth central passage 43. The cross sections of the actuator nut 37 and passage 43 are complementary (in one exemplary construction, this cross section was hexagonal). This way, the nut 37 slides freely through the passage 43, but turns when the dial plate 40 is turned. This is important because the housing carries the entire weight of the range dial mechanism 26 and the actuator pin 36, 37 is not loaded by its inertia. action does not become sluggish.

The remaining parts of the range dial mechanism 26 are a retaining washer 45, a gear 46, a loading spring 47, and an index or indicator plate 48. In one construction, gear 46 was made of nylon. These components will be understood best by a step-by-step description of how the actuator and range dial are assembled. First, the bushing 42 is fitted through the hole 25 in the upper half 23 of the housing. Then, while the bushing is held in place, the index plate 48 is placed so that its four depending feet, (such as 49) are fitting on either side of the upper housing half 23. The hole 50 in plate 48 fits over and is larger than the part of the bushing 42 which is projecting above the top of the housing 23.

Next, the loading spring 47 is fitted onto the bushing 42 to maintain a fairly tight assembly and to provide a degree of friction which tends to restrain the dial plate 40 against unwanted rotation.

The gear 46 is placed on the bushing 42, and the dial plate 40 is placed on top of the gear. On gear 46 are a circular series of upstanding lugs 52 which project upwardly through a hole 53 in the dial plate 40. Finally, the actuator assembly is fastened together when the restraining washer 45 is forced onto the bushing 42. The upstanding gear lugs 52 project upwardly between the tabs (such as 55) of the restraining washer. The ends of these tabs bite into the bushing 42 to prevent an unwanted disassembly of the range dial mechanism 26.

The actuator nut 37 is turned onto the threaded pin 36. Then, the upper housing half 23 is turned upside down and actuator nut 37 is dropped through the passage 43 in bushing 42. The actuator presser foot 35 has dimensions such that it fits loosely inside the housing 23 so that it moves up and down when the top of nut 37 is pushed, but does not turn when the actuator nut 37 turns.

This completes the assemblies associated with the upper half 23 of the housing.

The lower half 24 of the housing has the three lugs 29- 31 molded therein. Each lug is tapped and threaded on its lower end to receive a screw (such as 56). A somewhat dish-shaped, semi-circular plate 57 may be fitted over screw 56 to facilitate attaching and connecting an electrical wire (not shown). Similar parts for making other electrical connections are shown at 58-61.

The upper ends of the lugs 29-31 are shaped (as at 62) to form a cylindrical rivet. When in place, the rivet end 62 projects upward through housing 24 at 64. In like manner, the rivet ends 65, 66 project upwardly through holes 67, 68, respectively.

Thus, the snap The leaf spring assembly 22 includes three parallel tines 70, 71, 72 for supporting an electrical contact 74. A fulcrum plate 75 attaches to the leaf spring in a manner such that the center tine 71 is held in tension and the two outside tines 70, 72 are held in compression. This gives the two outside tines 70, 72 a somewhat arcuate shape and the center tine a flat shape. These shapes cooperate with each other to provide an over center spring bias which cause the snap action. For example, FIG. 4 shows a side view of the leaf spring assembly 22 in its normal condition with the contact 74 in a raised position. FIG. 5 shows the same leaf spring in its off-normal condition with contact 74 in a lowered position. This over center snap action is well known to those skilled in the art. They will readily perceive how the spring is made to snap from the first to the second positions responsive to a downward pressure (here represented by the arrow Al) on the tensioned tine. This pressure is applied upon the leaf spring by the actuator presser foot 35 when the top of the actuator nut 37 is pushed. A metal bridge 76 partially surrounds the tension tine 71 of the spring to reduce the travel for operation. This feature is covered in my co-pending application entitled, Bridge for an Electrically Conductive Leaf Spring, Serial No. 414,735, filed Nov. 30, 1964, and assigned to the assignee of this invention.

The fulcrum plate is attached to the lower housing half 24 in a manner such that the leaf spring assembly 22 is supported as a cantilever arrangement. This form of support results because a hole 77 on the end of the fulcrum plate 75 is fitted over the rivet end 66 which is projecting upwardly through the hole 68 in housing half 24. Then, the rivet 66 is swaged to secure the parts together.

The other electrical contacts inside the housing are provided by an upper stationary contact '78 held in place by rivet 62 which projects upwardly through hole 64 and a lower stationary contact 79 held in place by rivet 65 which projects upwardly through hole 67. The contacts 78, 74, 79 cooperate with each other to provide a double pole, single throw switch. Electrical wires (not shown) are connected to the screws 56, 60, 61.

In any suitable manner, the assemblies mounted on the lower housing half 24 and the upper housing half 23 are fastened together in a cooperating arrangement whereby actuator plate 35 rests upon the tension tine.

An important feature of the invention is that the actuator nut 37 may be rotated as much or as little as is required to calibrate any given switch to a given range of operations. (By range, I mean the allowed variations in the length of the actuator stroke required before the switch operates.) Then, the dial plate 40 is cemented to the retaining washer 4S and, therefore, also to the gear 46. The actuator nut 37 is now restrained to rotate over approximately the 360 of a single turn. This restraint results when a tab 80 on the dial plate 40 strikes against the lug 81 on the index plate 48 to provide limit locks. A pointer 82 on the index plate 48 records the actual operating point of the snap action by pointing at a notation on scale 41.

An advantage of this arrangement is that a single switch may be used in connection with any appropriate associated equipment despite a wide range of operational requirements of such equipment. The range of operation required by that equipment is selected before the dial plate 40 is cemented to the retaining washer 45. This way, the invention may be used to simplify the associated equipment and make it more reliable.

FIG. 3 shows a thermostat to illustrate an exemplary use of the snap action switch. The thermostat includes a temperature responsive power element 83, here represented as a housing 84 which encloses a bi-metal strip 85 which moves to the right or left (as viewed in FIG. 3) as a function of ambient temperature changes. This strip is mounted on the outside and the snap action switch is mounted on the inside of a box 86. The orientation and support are such that the nut 37 of the actuator pin plunger bears against the strip 85. The dial plate 40 has already been cemented in place to establish the range of operation required for this particular thermostat (i.e. over the entire operating range, the switch will snap responsive to a stroke having an excursion length which can be produced by the strip movement). However, the user will want to make fine adjustments. For example, he may want to turn up the heat during the day and turn down the heat at night.

Means are provided to make such a fine adjustment of the operating point from a remote location. To illustrate how this is done, FIG. 3 shows a gear 87 connected to a shaft 88. This gear meshes with the gear 46 associated with the range dial of the snap action switch. A retaining shackle 89 rotatably attaches one end of the shaft 88 to the snap action switch housing 20. The shackle is held in place by bolts passing through the holes 27, 28 in the lower housing half 24. The other end of the shaft 88 extends through and is rotatably secured by a hole in the box 86. Indicator means, here shown as a knob 90 is attached to the end of the shaft 88 which projects outside the box.

To facilitate a setting of the thermostat to a specific temperature, a temperature scale (not shown) is associated with knob 90. That is, a rotation of the knob 90 to point to 75, for example, turns shaft 88, gears 87, 46 and, therefore, the actuator nut 37. This adjusts the length of the stroke required to operate the switch so that the switch snaps when the strip 85 moves to a given position responsive to an ambient temperature of 75. It should be noted that this showing of a shaft and gear is intended as a generic disclosure of any suitable remote control device. Other instrumentalities may also be used, such as an electro-mechanical stepping device, for example.

The operation should now be apparent. All switches are made from the same piece parts regardless of the requirements of associated control devices. However, during construction, each of the switches is given a range of operation which allows the switch to operate with a single-and perhaps uniquetype of control device. Then, the range dial is locked in the selected operating range by cement applied over the retaining washer 45. Thus, the user may turn knob 90 and shaft 88 to rotate the dial 40 and thereby select any specific operating point within the range.

While the principles of the invention have been described above in connection with specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.

I claim:

1. A snap acting switch comprising a self-biased monostable leaf spring assembly comprising a plurality of spaced parallel tines, at least one of said tines being held in tension and at least one of said tines being held in compression, pin plunger means for mechanically applying an excursion inducing force to said spring, said pin plunger means including a threaded pin having an elongated threaded nut turned thereon, whereby the length of said pin plunger is fixed by the number of turns taken by said nut on said threaded pin, means for mounting said leaf spring in a position such that said self-bias automatically moves said spring to a normal stable position when said pin plunger is not actuated and said spring snaps to an off-normal position when said pin plunger is actuated, and range setting means for adjusting the length of the pin plunger to select a point in the plunger travel where said spring snaps to said off-normal position, said range setting means comprising a dial plate having a gear attached thereto, a smooth central passage passing through said dial plate and gear, the said nut passing through said central passing and being free to slide therein for reciprocal movement independent of the inertia of said range setting means.

2. The switch of claim 1 wherein said nut is initially rotated to any desired position relative to said dial, and means for thereafter restraining said nut to rotation with said dial.

3. The switch of claim 2 and limit lock means associated with said dial for limiting the allowed rotation of said nut.

4. A snap action switch comprising a housing for providing an enclosure that is protected against contaminants, a self-biased monostable snap action leaf spring assembly mounted inside said enclosure, actuator means comprising a pin plunger assembly extending through a hole in said housing for applying a force to snap said spring from its normal monostable position to an offnormal position, said pin plunger assembly including a presser foot having an upstanding threaded pin attached thereto and an elongated threaded nut turned onto said threaded pin, means mounted on said housing for selecting any point in a range of points along the length of the actuator stroke where said pin plunger assembly snaps said spring to said off-normal position, the pin plunger being free to move independently of the selector means, said selector means including a range dial attached to said housing, said dial having an associated smooth central passage aligned with the hole in the housing through which said nut passes, the cross sections of said passage and said nut being complementary so that said nut slides freely through said passage but turns with said dial to adjust the length of said pin plunger assembly and thereby fix the operating point of said switch, and gear means connected to said range dial for turning said nut responsive to controls received from a remote location.

5. The switch of claim 4 including a shaft having a gear attached to one end for driving said gear means and an indicator attached to the other end.

6. A switch comprising: a leaf spring actuator means for applying an excursion inducing force to move said spring from a normal position to an off-normal position, said means including a threaded pin having one end for engaging said spring and an elongated threaded nut partially turned onto said threaded pin whereby the combined length of the pin and nut is fixed by the number of turns taken by the nut on the pin, the outer end of the nut forming a surface for receiving the switch actuating force, means formed on said pin for preventing rotation of the pin, and means for providing a range of adjustments of the point in the axial movement of said pin and nut where said spring moves from said normal position to said off-normal position, said adjustment means including an axially fixed, rotatable dial assembly having a smooth central passage through which said nut passes, the cross-sections of the passage and the nut being complementary so that the actuator axially slides freely within the passage without the inertia of the adjustment means, but the nut turns with the dial, whereby the combined length of said pin and nut changes as the dial is rotated and hence the operating point of the switch is adjusted.

References Cited by the Examiner UNITED STATES PATENTS 2,511,271 6/1950 Kaminky et al. 3,069,916 12/1962 Watson. 3,097,273 7/ 1963 Denner.

FOREIGN PATENTS 962,745 7/ 1964 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner. KATHLEEN H. CLAFFY, Examiner. D. SMITH JR., Assistant Examiner. 

1. A SNAP ACTING SWITCH COMPRISING A SELF-BIASED MONOSTABLE LEAF SPRING ASSEMBLY COMPRISING A PLURALITY OF SPACED PARALLEL TINES, AT LEAST ONE OF SAID TINES BEING HELD IN TENSION AND AT LEAST ONE OF SAID TINES BEING HELD IN COMPRESSION, PIN PLUNGER MEANS FOR MECHANICALLY APPLYING AN EXCURSION INDUCING FORCE TO SAID SPRING, SAID PIN PLUNGER MEANS INCLUDING A THREADED PIN HAVING AN ELONGATED THREADED NUT TURNED THEREON, WHEREBY THE LENGTH OF SAID PIN PLUNGER IS FIXED BY THE NUMBER OF TURNS TAKEN BY SAID NUT ON SAID THREADED PIN, MEANS FOR MOUNTING SAID LEAF SPRING IN A POSITION SUCH THAT SAID SELF-BIAS AUTOMATICALLY MOVES SAID SPRING TO A NORMAL STABLE POSITION WHEN SAID PIN PLUNGER IS NOT ACTUATED AND SAID SPRING SNAPS TO AN OFF-NORMAL POSITION WHEN SAID PIN PLUNGER IS ACTUATED, AND RANGE SETTING MEANS FOR ADJUSTING THE LENGTH OF THE PIN PLUNGER TO SELECT A POINT IN THE PLUNGER TRAVEL 